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How
to Choose a Pesticide Residue Testing Lab
(By Diane Baxter,
from June 1986 Pesticides
and You)
When do you
need a laboratory?
If you foresee finding
yourself in court, because of property damage or possible health effects,
you will need to document pesticide exposure.
Will positive
results establish a link between health effects and pesticide exposure?
Not necessarily.
Although cause and effect are difficult to establish, testing may detect
the presence of the chemical in the physical or biological environment,
thus strengthening a case.
Environmental testing--soil,
water, air, surface swabs, wood scrapings, carpet samples, etc., and/or
Biological testing--blood,
urine, even fat biopsies.
The biological tests
required depend on the chemical involved. For example, a blood test can
detect acetylcholinesterase enzyme depression caused by organophosphate
poisoning. Phenoxy acid residues, however, are measured in the urine.
Organochlorines can sometimes be detected in the blood, but 100 to 300
times more may be detected in fat tissue.
What analytical
methodology must the laboratory be able to perform?
The lab should
be using validated methods of analysis for the particular pesticide, such
as those published in the Pesticide Analytical Manual, in the Association
of Official Analytical Chemists Manual, or by EPA. It should have an internal
quality assurance program in place to make sure instruments and personnel
are performing well. Check samples should be run on positive or borderline
positive samples.
What
else should you know about the method used to detect pesticide residues?
In consultation
with an independent scientist, either a toxicologist or an analytical
chemist, determine how sensitive the method of analysis must be to be
useful to you, and then determine whether the lab can perform reliable
measurements at that level.
How should results
be reported to me?
Numerical data
should be reported in clearly identifiable units, for example, milligrams
per liter, parts-per-million, etc. The laboratory should provide you with
information about the adequacy of the method chosen for analysis, including
percent recovery of spiked samples, results of a standard curve, and results
of assay blanks.
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